Recursion 3 Solution in C#

This Page Contains the Solution in C# Programming Language for the Day 9 : Recursion 3, Code Challange of the HackerRank 30 Days of Code.

using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization;
using System.Text.RegularExpressions;
using System.Text;
using System;

class Result
{
    /*
     * Complete the 'factorial' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts INTEGER n as parameter.
     */

    public static int factorial(int n)
    {
        if (n == 1) return 1;
        return factorial(n - 1) * n;
    }
}

class Solution
{
    public static void Main(string[] args)
    {
        TextWriter textWriter = new StreamWriter
        (@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);

        int n = Convert.ToInt32(Console.ReadLine().Trim());

        int result = Result.factorial(n);

        textWriter.WriteLine(result);

        textWriter.Flush();
        textWriter.Close();
    }
}